From b12bb6110302f66b6105568fb6980834c375dbc6 Mon Sep 17 00:00:00 2001
From: Daira Hopwood <daira@jacaranda.org>
Date: Mon, 6 Jun 2022 18:40:58 +0100
Subject: [PATCH] =?UTF-8?q?An=20[NU5=20onward]=20consensus=20rule=20requir?=
 =?UTF-8?q?ing=20the=20`nConsensusBranchId`=20field=20to=20match=20the=20c?=
 =?UTF-8?q?onsensus=20branch=20ID=20used=20for=20SIGHASH=20transaction=20h?=
 =?UTF-8?q?ashes,=20should=20apply=20only=20when=20effectiveVersion=20?=
 =?UTF-8?q?=E2=89=A5=205=20(since=20v4=20transactions=20did=20not=20explic?=
 =?UTF-8?q?itly=20encode=20the=20`nConsensusBranchId`=20field.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
---
 protocol/protocol.tex | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/protocol/protocol.tex b/protocol/protocol.tex
index ec588d7a..288b6113 100644
--- a/protocol/protocol.tex
+++ b/protocol/protocol.tex
@@ -12575,8 +12575,8 @@ in \cite{ZIP-239}.
   \nufiveonwarditem{The \transactionVersionNumber \MUST be $4$ or $5$.
         If the \transactionVersionNumber{} is $4$ then the \versionGroupID \MUST be $\hexint{892F2085}$.
         If the \transactionVersionNumber{} is $5$ then the \versionGroupID \MUST be $\hexint{26A7270A}$.}
-  \nufiveonwarditem{The \nConsensusBranchId{} field \MUST match the \consensusBranchID used for
-        \sighashTxHashes, as specified in \cite{ZIP-244}.}
+  \nufiveonwarditem{If $\effectiveVersion \geq 5$, the \nConsensusBranchId{} field \MUST match the
+        \consensusBranchID used for \sighashTxHashes, as specified in \cite{ZIP-244}.}
   \presaplingitem{The encoded size of the \transaction \MUST be less than or equal to
         $100000$ bytes.}
   \nufiveonwarditem{\nSpendsSapling, \nOutputsSapling, and \nActionsOrchard{} \MUST all be less
@@ -14635,11 +14635,19 @@ Peter Newell's illustration of the Jubjub bird, from \cite{Carroll1902}.
 \intropart
 \lsection{Change History}{changehistory}
 
-\historyentry{2022.3.2}{2022-05-11}
+\historyentry{2022.3.2}{}
 \begin{itemize}
-  \item \nufive{Set $\NUFiveActivationHeight$ for \Testnet and \Mainnet.} 
+\nufive{
+    \item Set $\NUFiveActivationHeight$ for \Testnet and \Mainnet.
+    \item An [\NUFive onward] consensus rule requiring the \nConsensusBranchId{}
+          field to match the \consensusBranchID used for \sighashTxHashes, should
+          apply only when $\effectiveVersion \geq 5$ (since v4 \transactions did
+          not explicitly encode the \nConsensusBranchId{} field).
+}
+    \item No changes before \NUFive.
 \end{itemize}
 
+
 \historyentry{2022.3.1}{2022-04-28}
 \begin{itemize}
 \nufive{